Limiting mobility between networks based on cell id

ABSTRACT

Restricting mobility between networks by identifying and rejecting incoming mobility events (e.g. handovers) from unknown cell sites based on a cellID included in a handover request. Core network nodes e.g. MME, AMF, SMF, can detect and reject the incoming mobility events by comparing Cell ID with a white list or referring to a database. This improves over current 3GPP specifications and network vendor implementations that support restriction policies on the source but not on the target.

This patent application is a continuation of U.S. patent applicationSer. No. 17/406,338, filed on Aug. 19, 2021, which is incorporated byreference in its entirety for all purposes.

TECHNICAL BACKGROUND

As communication networks evolve and grow, there are ongoing challengesin communicating data across different types of networks. Differenttypes of networks can include wireless networks, packet-switchednetworks such as the internet, satellite networks, public/privatenetworks, local area networks (LANs), wide area networks (WANs), and anynetwork enabling communication between different types of electronicdevices. Other types of communication networks in various combinationsmay be envisioned by those having ordinary skill in the art in light ofthis disclosure. One type of communication network described hereinincludes telecommunications networks, such as 5G New Radio (NR)networks, 4G LTE networks, etc. Such networks utilize specializeddevices, such as gateways, routers, switches, etc. that enablecommunication between sub-network types, such as radio access networks(RANs), core networks, and so on, as further described herein. Forexample, consumer wireless devices (e.g. cellular telephones,smartphones, tablets, etc.) can attach to radiofrequency (RF) carriersdeployed by access nodes within a coverage area of a RAN, and exchangedata transmissions and signals between core network components, publicdata networks, and other combinations of networks and wireless devices.However, there exist issues with handovers and mobility of wirelessdevices between different types of networks and carriers deployedtherefrom. For example, information shared between networks tofacilitate handovers can be exploited by malicious network elements oroperators.

OVERVIEW

Examples described herein include methods and systems for restrictingmobility between networks based on cellular identifiers (cellID). Anexample method described herein includes receiving, at a first corenetwork node associated with a first radio access network (RAN), a firsthandover request from a second core network node associated with asecond RAN, the first handover request being for a first wireless deviceon the second RAN, determining, by the first core network node, that afirst cell identifier in the first handover request does not match awhitelist of cell identifiers stored on the first core network node, andrejecting the first handover request.

An example system described herein includes a first core network nodeassociated with a first network and a processor communicably coupled tothe first core network node. The processor enables the first corenetwork node to perform operations comprising receiving a first handoverrequest for a wireless device from a second core network node associatedwith a second network, determining that a first cell identifier in thefirst handover request does not match a whitelist of cell identifiersstored on the first core network node, and rejecting the first handoverrequest.

An example processing node for limiting mobility includes a processorand a memory that enable the processing node to perform operationsincluding receiving, at a first core network node associated with afirst radio access network (RAN), a first handover request from a secondcore network node associated with a second RAN, the first handoverrequest being for a first wireless device on the second RAN,determining, by the first core network node, that a first cellidentifier in the first handover request does not match a whitelist ofcell identifiers stored on the first core network node, and rejectingthe first handover request.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 depicts an example of a system for limiting mobility betweennetworks.

FIG. 2 depicts an example controller node for limiting mobility betweennetworks.

FIG. 3 depicts an example of a method for limiting mobility betweennetworks.

FIG. 4 depicts an example of limiting mobility between networks usingdifferent RATs.

FIG. 5 depicts another example of limiting mobility between networksusing different RATs.

DETAILED DESCRIPTION

Methods and systems for restricting mobility between networks canidentify and reject incoming mobility events (e.g. handovers) fromunknown cell sites based on a cellular identifiers (e.g. cellID). ThecellID can be included in a handover request, and core network node on adestination network, such as mobility management entity (MME) in 4G LTEnetworks, or access and mobility function (AMF) in 5G NR networks, canbe configured to detect and reject the incoming mobility events bycomparing with a white list or referring to a database. This provides animprovement over current 3GPP specifications and network vendorimplementations, which support certain restriction policies on thesource side, but not on the target side.

Therefore, a method described herein for restricting mobility includesreceiving, at a first core network node associated with a first radioaccess network (RAN), a first handover request from a second corenetwork node associated with a second RAN, the first handover requestbeing for a first wireless device on the second RAN, determining, by thefirst core network node, that a first cell identifier in the firsthandover request does not match a whitelist of cell identifiers storedon the first core network node, and rejecting the first handoverrequest. In examples described herein, the first and second RANs can beon the same or different networks. Further, cell IDs in handoverrequests may be associated with different tracking areas or coverageareas of each RAN. Thus, network operators can use this method to carveout portions of service areas that are “allowed” or white-listed formobility of wireless devices. This can be useful for enterprise trackingareas, network slicing, etc. Further, the whitelist can be provided tothe first core network node by one or more network operators or sharedbetween the first and second core network nodes. While handovers may beallowed at other network nodes based on other factors (signal levels,home subscriber servers, etc.), the disclosed operations enablepreventing handovers at specific core network nodes, such as mobilitymanagement entities (MME) or access and mobility functions (AMF).

FIG. 1 depicts a system 100 comprising a communication network 101,gateways 102 a and 102 b, controller nodes 104 a and 104 b, access nodes110 a and 120 b, and wireless device 130. Access nodes 110 a/b can bepart of different radio access networks (RAN). In one example, accessnodes 110 a/b may be macrocell access nodes configured to deploy one ormore wireless air interfaces to which wireless device 130 canrespectively attach and access network services from network 101. Forexample, access nodes 110 a/b can include an eNodeB, or a gNodeB, and isconfigured to deploy a wireless air interface one or more radio accesstechnologies (RATs) such as 4G LTE and/or 5G NR. Each RAT can beconfigured to utilize a different frequency band or sub-band, adifferent channel size or bandwidth, and so on. Further, controllernodes 104 a/b and gateways 102 a/b can respectively each be associatedwith the different RANs containing access nodes 110 a/b. For example,controller node 104 a and gateway 102 a can be part of a first corenetwork associated with access node 110 a, and controller node 104 b andgateway 102 b can be part of a second core network associated withaccess node 110 b. In a 4G LTE network, controller node 104 a/b can be amobility management function (MMF) and gateways 102 a/b can be one ormore serving gateways (S-GW), packet gateways (P-GW), and so on.Conversely, in a 5G NR network, controller node 104 a/b can be an accessand mobility session management (AMF) and/or session management function(SMF), and gateways 102 a/b can be one or more user plane functions(UPF). Hereinafter, the term “core network node” can be used to refer toany combination of MME, SMF, AMF, gateway(s), etc., and are not limitedto a specific network implementation. Although only access nodes 110a/b, controller nodes 104 a/b, gateways 102 a/b, and wireless device 130are illustrated in FIG. 1 , system 100 can include various othercombinations of core network nodes carriers/wireless air interfaces,antenna elements, access nodes, and wireless devices, as may be evidentto those having ordinary skill in the art in light of this disclosure.

In an exemplary embodiment, system 100 is further configured to identifyand reject incoming mobility events, such as a handover of wirelessdevice 130 from access node 110 b to access node 110 a. For example,access node 110 b may be in a coverage area that is not supported byaccess node 110 a (and/or networks associated therewith). In oneexample, a whitelist stored on data store 105 a can contain a pluralityof cellular identifiers (e.g. cellID) associated with of known orsupported cell sites, access nodes, or networks. Each incoming handoverrequest can include an identifier of a source cell, and identified byreferring to the whitelist. If there is no match, the incoming handoverrequest (or related mobility event) is rejected.

For example, a method performed by one or more network nodes withinsystem 100 can include receiving, at a first core network node (e.g.controller node 104 a) associated with a first RAN (e.g. first RANcomprising access node 110 a), a first handover request from a secondcore network node (e.g. controller node 104 b) associated with a secondRAN (e.g. second RAN comprising access node 110 b). The handover requestcan be for a wireless device 130 on the second RAN (e.g. attached toaccess node 110 b), determining, by the first core network node (e.g.controller node 104 a), that a first cell identifier in the handoverrequest does not match a whitelist of cell identifiers stored thereon,and rejecting the handover request.

Although separate, the first and second RANs can be on the same ordifferent networks, e.g. as part of a heterogeneous network with a largeenough geographic area to require different core network elements.Further, cell IDs in handover requests may be associated with differenttracking areas or coverage areas of each RAN. Thus, network operatorscan use this method to carve out portions of service areas that are“allowed” or white-listed for mobility of wireless devices. This can beuseful for enterprise tracking areas, network slicing, etc. Further, thewhitelist can be provided to the first core network node (e.g.controller node 104 a) by one or more network operators, or sharedbetween the first and second core network nodes (e.g. by virtue of beingstored on data store 105 b or any other network node in communicationwith core network nodes 104 a/b).

Access nodes 110 a/b can be any network node configured to providecommunication between wireless device 130 and communication network 101,including standard access nodes and/or short range, low power, smallaccess nodes. For instance, access nodes 110 a/b may include anystandard access node, such as a macrocell access node, base transceiverstation, a radio base station, next generation or gigabit NodeBs (gNBs)in 5G networks, or enhanced eNodeBs (eNBs) in 4G/LTE networks, or thelike. In an exemplary embodiment, a macrocell access node can have acoverage area in the range of approximately five kilometers to thirtyfive kilometers and an output power in the tens of watts. In otherembodiments, access nodes 110 a/b can be a small access node including amicrocell access node, a picocell access node, a femtocell access node,or the like such as a home NodeB or a home eNodeB device. Moreover, itis noted that while access nodes 110 a/b are illustrated in FIG. 1 , anynumber of access nodes can be implemented within system 100.

Access nodes 110 a/b can comprise processors and associated circuitry toexecute or direct the execution of computer-readable instructions toperform operations such as those further described herein. Briefly,access nodes 110 a/b can retrieve and execute software from storage,which can include a disk drive, a flash drive, memory circuitry, or someother memory device, and which can be local or remotely accessible. Thesoftware comprises computer programs, firmware, or some other form ofmachine-readable instructions, and may include an operating system,utilities, drivers, network interfaces, applications, or some other typeof software, including combinations thereof. Further, access nodes 110a/b can receive instructions and other input at a user interface. Accessnodes 110 a/b communicate with gateway nodes 102 a/b and controllernodes 104 a/b via various communication links and interfaces furtherdescribed herein. Access nodes 110 a/b may communicate with each other(and with other access nodes not shown herein) using a direct link suchas an X2 link or similar.

Wireless device 130 may be any device, system, combination of devices,or other such communication platform capable of communicating wirelesslywith access nodes 110 a/b using one or more frequency bands deployedtherefrom. Wireless device 130 may be, for example, a mobile phone, awireless phone, a wireless modem, a personal digital assistant (PDA), avoice over internet protocol (VoIP) phone, a voice over packet (VOP)phone, or a soft phone, as well as other types of devices or systemsthat can exchange audio or data via access nodes 110 a/b. Other types ofcommunication platforms are possible.

Communication network 101 can be a wired and/or wireless communicationnetwork, and can comprise processing nodes, routers, gateways, andphysical and/or wireless data links for carrying data among variousnetwork elements, including combinations thereof, and can include alocal area network a wide area network, and an internetwork (includingthe Internet). Communication network 101 can be capable of carryingdata, for example, to support voice, push-to-talk, broadcast video, anddata communications by wireless device 130. Wireless network protocolscan comprise MBMS, code division multiple access (CDMA) 1×RTT, GlobalSystem for Mobile communications (GSM), Universal MobileTelecommunications System (UMTS), High-Speed Packet Access (HSPA),Evolution Data Optimized (EV-DO), EV-DO rev. A, Third GenerationPartnership Project Long Term Evolution (3GPP LTE), WorldwideInteroperability for Microwave Access (WiMAX), Fourth Generationbroadband cellular (4G, LTE Advanced, etc.), and Fifth Generation mobilenetworks or wireless systems (5G, 5G New Radio (“5G NR”), or 5G LTE).Wired network protocols that may be utilized by communication network101 comprise Ethernet, Fast Ethernet, Gigabit Ethernet, Local Talk (suchas Carrier Sense Multiple Access with Collision Avoidance), Token Ring,Fiber Distributed Data Interface (FDDI), and Asynchronous Transfer Mode(ATM). Communication network 101 can also comprise additional basestations, controller nodes, telephony switches, internet routers,network gateways, computer systems, communication links, or some othertype of communication equipment, and combinations thereof.

Communication links used within system 100 can include variouscommunication media, such as air, space, metal, optical fiber, or someother signal propagation path—including combinations thereof. Thecommunication links can be wired or wireless and use variouscommunication protocols such as Internet, Internet protocol (IP),local-area network (LAN), optical networking, hybrid fiber coax (HFC),telephony, T1, or some other communication format—includingcombinations, improvements, or variations thereof. Wirelesscommunication links can be a radio frequency, microwave, infrared, orother similar signal, and can use a suitable communication protocol, forexample, Global System for Mobile telecommunications (GSM), CodeDivision Multiple Access (CDMA), Worldwide Interoperability forMicrowave Access (WiMAX), Long Term Evolution (LTE), 5G NR, orcombinations thereof. Communication links can also include proprietaryor standardized interfaces, such as S1, S5, S6 . . . etc. interfaces.Other wireless protocols can also be used. Communication links can be adirect link or might include various equipment, intermediate components,systems, and networks. Communication links may comprise many differentsignals sharing the same link. Communication links may be associatedwith many different reference points, such as N1-Nxx, as well as S1-Sxx,etc. In one example, core network nodes 104 a and 104 b can communicateover a communication link 106 that comprises a N26 interface, orequivalent. N26 is an inter-control-node interface between AMF and MMEto enable interworking between the 4G LTE and 5G NR core networks.Interworking procedures using the N26 interface enable the exchange ofmobility management and session management states between the source andtarget networks (e.g. between access node 110 b and 110 a), includinghandover procedures.

Gateway nodes 102 a/b can be any network node configured to interfacewith other network nodes using various protocols. Gateway nodes 102 a/bcan communicate user data over system 100. Gateway nodes 102 a/b can bea standalone computing device, computing system, or network component,and can be accessible, for example, by a wired or wireless connection,or through an indirect connection such as through a computer network orcommunication network. For example, gateway nodes 102 a/b can include aserving gateway (SGW), a public data network gateway (PGW), and/or asystems architecture evolution gateway (SAE-GW) associated with 4G LTEnetworks, or a user plane function (UPF) associated with 5G NR networks.One of ordinary skill in the art would recognize that gateway nodes 102a/b is not limited to any specific technology architecture, such as LongTerm Evolution (LTE) or 5G NR, and can be used with any networkarchitecture and/or protocol.

Gateway nodes 102 a/b can comprise a processor and associated circuitryto execute or direct the execution of computer-readable instructions toobtain information. Gateway nodes 102 a/b can retrieve and executesoftware from storage, which can include a disk drive, a flash drive,memory circuitry, or some other memory device, and which can be local orremotely accessible. The software comprises computer programs, firmware,or some other form of machine-readable instructions, and may include anoperating system, utilities, drivers, network interfaces, applications,or some other type of software, including combinations thereof. Gatewaynodes 102 a/b can receive instructions and other input at a userinterface.

Controller nodes 104 a/b can be any network node configured tocommunicate information and/or control information over system 100.Controller nodes 104 a/b can be configured to transmit controlinformation associated with a mobility event, e.g. a handover.Controller nodes 104 a/b can be a standalone computing device, computingsystem, or network component, and can be accessible, for example, by awired or wireless connection, or through an indirect connection such asthrough a computer network or communication network. For example,controller nodes 104 a/b can include a mobility management entity (MME),a control gateway (SGW-C or PGW-C), a session management function (SMF),access and mobility function (AMF), a home subscriber server (HSS), apolicy control and charging rules function (PCRF), an authentication,authorization, and accounting (AAA) node, a rights management server(RMS), a subscriber provisioning server (SPS), a policy server, etc. Oneof ordinary skill in the art would recognize that controller nodes 104a/b is not limited to any specific technology architecture, such as LongTerm Evolution (LTE) or 5G NR, and can be used with any networkarchitecture and/or protocol.

Controller nodes 104 a/b can comprise a processor and associatedcircuitry to execute or direct the execution of computer-readableinstructions to obtain information. Controller nodes 104 a/b canretrieve and execute software from storage, which can include a diskdrive, a flash drive, memory circuitry, or some other memory device, andwhich can be local or remotely accessible. In an exemplary embodiment,each controller node 104 a/b respectively includes a database 105 a/bfor storing information, such as whitelists, cell IDs associated withaccess nodes 110 a and 110 b (and other access nodes within system 100),and so on. This information may be requested by or shared with accessnodes 110 a/b via communication links 106, 107, X2 connections, and soon. The software comprises computer programs, firmware, or some otherform of machine-readable instructions, and may include an operatingsystem, utilities, drivers, network interfaces, applications, or someother type of software, and combinations thereof. Controller nodes 104a/b can receive instructions and other input at a user interface.

Other network elements may be present in system 100 to facilitatecommunication but are omitted for clarity, such as base stations, basestation controllers, mobile switching centers, dispatch applicationprocessors, and location registers such as a home location register orvisitor location register. Furthermore, other network elements that areomitted for clarity may be present to facilitate communication, such asadditional processing nodes, routers, gateways, and physical and/orwireless data links for carrying data among the various networkelements, e.g. between access nodes 110 a/b and communication network101.

Further, the methods, systems, devices, networks, access nodes, andequipment described herein may be implemented with, contain, or beexecuted by one or more computer systems and/or processing nodes. Themethods described above may also be stored on a non-transitory computerreadable medium. Many of the elements of communication system 100 maybe, comprise, or include computers systems and/or processing nodes,including access nodes, controller nodes, and gateway nodes describedherein. In some examples, a processing node may comprise (or becommunicatively coupled to) a core network node, such as controllernode(s) 104 a/b.

FIG. 2 depicts an exemplary controller node 200 for limiting mobilitybetween networks. Controller node comprises a processor 211, a memory212, a whitelist 213, and interfaces 214. Processor 211 can include acentral processing unit (CPU), and memory 212 can include a disk drive,flash drive, memory circuitry, or other memory device. Memory 212 canstore computer programs, firmware, or some other form ofmachine-readable instructions, including an operating system, utilities,drivers, network interfaces, applications, or some other type ofsoftware. Further, memory 212 can store software or computer-readableinstructions that can be executed to perform the operations describedherein. For example, memory 212 can include instructions for matching awhitelist 213 of cell identifiers stored on the controller node 210, andrejecting a handover request that does not include a whitelisted cellidentifier. Since cell IDs in handover requests may be associated withdifferent tracking areas or coverage areas of each RAN, networkoperators can use this method to carve out portions of service areasthat are “allowed” or white-listed for mobility of wireless devices. Thewhitelist 213 can be provided to the controller node 210 by one or morenetwork operators or shared by another core network node. As describedherein, core network node 210 can include a one or more of a MME, AMF,or equivalent. Thus, interfaces 214 can be associated with differentreference points, such as N1-Nxx, as well as S1-Sxx, X2, etc., or anyinterface enabling controller node 210 to communicate with other networkelements. Controller node 210 may further include other components suchas a power management unit, a control interface unit, user interface,etc., which are omitted for clarity.

FIG. 3 depicts an exemplary method for limiting mobility in wirelessnetworks. The operations of FIG. 3 may be performed by one or moreprocessing nodes or core network nodes. Although FIG. 3 depicts stepsperformed in a particular order for purposes of illustration anddiscussion, the operations discussed herein are not limited to anyparticular order or arrangement. One skilled in the art, using thedisclosures provided herein, will appreciate that various steps of themethods can be omitted, rearranged, combined, and/or adapted in variousways.

At 31, a handover request is received at a first core network nodeassociated with a first RAN. In an example, the handover request can beany mobility event associated with a handover or a request to handover awireless device from a second RAN to the first RAN associated with thefirst core network node. A cellular identifier (e.g. CellID) can beincluded in the handover request, and at 32, the core network node (e.g.MME or AMF) can be configured to determine that the cell identifier doesnot match a whitelist and, at 33, reject or deny the incoming mobilityevents. The first and second RANs can be on the same or differentnetworks. Further, cell IDs in handover requests may be associated withdifferent tracking areas or coverage areas of each RAN. Thus, networkoperators can use this method to carve out portions of service areasthat are “allowed” or white-listed for mobility of wireless devices.This can be useful for enterprise tracking areas, network slicing, etc.Further, the whitelist can be provided to the first core network node byone or more network operators or shared between the first and secondcore network nodes. While handovers may be allowed at other networknodes based on other factors (signal levels, home subscriber servers,etc.), the disclosed operations enable preventing handovers at specificcore network nodes.

Conversely, a second handover request can be received at the corenetwork node from a second core network node. The second handoverrequest can be associated with a second wireless device that is from atracking area or cell ID that is authorized or allowed. In this case,the core network node (e.g. MME or AMF depending on networkimplementation) can determine that the cell identifier in the secondhandover request matches the whitelist of cell identifiers stored on thecore network node, and accept/allow the second handover request.Accepting the second handover request can also include updating othercore network nodes that the second handover request was accepted.

FIG. 4 depicts exemplary limitation on mobility from a 4G LTE network toa 5G NR network. Controller nodes 404 a and 404 b are respectivelycoupled to access nodes 410 a and 420 b, and wireless device 430 isillustrated as moving into a coverage area 415 a associated with accessnode 410 a from a coverage area 415 b associated with access node 410 b.Access nodes 410 a/b can be part of different radio access networks(RAN). In this example, access node 410 a comprises a gNodeB, and istherefore coupled to an AMF 404 a. Further, access node 410 b comprisesa eNodeB, and is therefore coupled to a MME 404 b. Each access node 410a/b may be a macrocell access node configured to deploy one or morewireless air interfaces to which wireless device 430 can respectivelyattach.

In this example, AMF 404 a is configured to identify and reject incomingmobility events, such as a handover of wireless device 430 from accessnode 410 b to access node 410 a. For example, access node 410 b may bein a coverage area 415 b that is not supported by access node 410 a(and/or networks associated therewith). In one example, a whiteliststored on AMF 404 a can contain a plurality of cellular identifiers(e.g. cellID) associated with of known or supported cell sites, accessnodes, or networks. Each incoming handover request can include anidentifier of a source cell, and identified by referring to thewhitelist. If there is no match, the incoming handover request (orrelated mobility event) is rejected. The handover information (or anymobility event information) can be transmitted from MME 404 b to AMF 404a via a communication link 406, which can comprise a N26 interface orequivalent. Further, cell IDs in handover requests may be associatedwith different tracking areas or coverage areas of each RAN. Thus,network operators can use this method to carve out portions of serviceareas that are “allowed” or white-listed for mobility of wirelessdevices.

FIG. 5 depicts exemplary limitation on mobility from a 4G LTE network toa 5G NR network. Controller nodes 504 a and 504 b are respectivelycoupled to access nodes 510 a and 520 b, and wireless device 530 isillustrated as moving into a coverage area 515 a associated with accessnode 510 a from a coverage area 515 b associated with access node 510 b.Access nodes 510 a/b can be part of different radio access networks(RAN). In this example, access node 510 a comprises a eNodeB, and istherefore coupled to an MME 504 a. Further, access node 510 b comprisesa eNodeB, and is therefore coupled to a AMF 504 b. Each access node 510a/b may be a macrocell access node configured to deploy one or morewireless air interfaces to which wireless device 530 can respectivelyattach.

In this example, MME 504 a is configured to identify and reject incomingmobility events, such as a handover of wireless device 530 from accessnode 510 b to access node 510 a. For example, access node 510 b may bein a coverage area 515 b that is not supported by access node 510 a(and/or networks associated therewith). In one example, a whiteliststored on MME 504 a can contain a plurality of cellular identifiers(e.g. cellID) associated with of known or supported cell sites, accessnodes, or networks. Each incoming handover request can include anidentifier of a source cell, and identified by referring to thewhitelist. If there is no match, the incoming handover request (orrelated mobility event) is rejected. The handover information (or anymobility event information) can be transmitted from AMF 504 b to MME 504a via a communication link 506, which can comprise a N26 interface orequivalent. Further, cell IDs in handover requests may be associatedwith different tracking areas or coverage areas of each RAN. Thus,network operators can use this method to carve out portions of serviceareas that are “allowed” or white-listed for mobility of wirelessdevices.

The exemplary embodiments described herein can be performed under thecontrol of a processing system executing computer-readable codesembodied on a computer-readable recording medium or communicationsignals transmitted through a transitory medium. The computer-readablerecording medium is any data storage device that can store data readableby a processing system, and includes both volatile and nonvolatilemedia, removable and non-removable media, and contemplates mediareadable by a database, a computer, and various other network devices.

Examples of the computer-readable recording medium include, but are notlimited to, read-only memory (ROM), random-access memory (RAM), erasableelectrically programmable ROM (EEPROM), flash memory or other memorytechnology, holographic media or other optical disc storage, magneticstorage including magnetic tape and magnetic disk, and solid statestorage devices. The computer-readable recording medium can also bedistributed over network-coupled computer systems so that thecomputer-readable code is stored and executed in a distributed fashion.The communication signals transmitted through a transitory medium mayinclude, for example, modulated signals transmitted through wired orwireless transmission paths.

The above description and associated figures teach the best mode of theinvention. The following claims specify the scope of the invention. Notethat some aspects of the best mode may not fall within the scope of theinvention as specified by the claims. Those skilled in the art willappreciate that the features described above can be combined in variousways to form multiple variations of the invention. As a result, theinvention is not limited to the specific embodiments described above,but only by the following claims and their equivalents.

1. A method, comprising: receiving, at a first core network nodeassociated with a first radio access network (RAN), a first handoverrequest from a second core network node associated with a second RAN,the first handover request being for a first wireless device on thesecond RAN; determining, by the first core network node, that a firstcell identifier in the first handover request matches an allowed list ofcell identifiers stored on the first core network node; and acceptingthe first handover request.
 2. The method of claim 1, wherein the firstRAN is configured to utilize a first radio access technology (RAT), andthe second RAN is configured to utilize a second radio access technology(RAT).
 3. The method of claim 2, wherein the first RAT comprises 5G, andthe second RAT comprises any of 4G, 5G, or 6G.
 4. The method of claim 3,wherein the first core network node comprises any of an access andmobility management function (AMF) or a mobility management entity(MME).
 5. The method of claim 3, wherein the second core network nodecomprises any of an access and mobility management function (AMF) or amobility management entity (MME).
 6. The method of claim 2, wherein thefirst RAT comprises 4G, and the second RAT comprises any of 4G, 5G, or6G.
 7. The method of claim 6, wherein the first core network nodecomprises any of an access and mobility management function (AMF) or amobility management entity (MME).
 8. The method of claim 6, wherein thesecond core network node comprises any of an access and mobilitymanagement function (AMF) or a mobility management entity (MME).
 9. Themethod of claim 1, further comprising: receiving, at the first corenetwork node, a second handover request from the second core networknode, the second handover request associated with a second wirelessdevice on the second RAN; determining, by the first core network node,that a second cell identifier in the second handover request does notmatch the allowed list of cell identifiers stored on the first corenetwork node; and rejecting the second handover request.
 10. The methodof claim 9, wherein accepting the second handover request comprisesupdating other core network nodes that the second handover request wasrejected.
 11. A system, comprising a target core network node associatedwith a target network operator; and a processor communicably coupled tothe target core network node, the processor for enabling the target corenetwork node to perform operations comprising: receiving a firsthandover request for a wireless device from a source core network nodeassociated with a source network operator; determining that a first cellidentifier in the first handover request matches an allowed list of cellidentifiers stored on the target core network node; and accepting thefirst handover request.
 12. The system of claim 11, wherein the targetnetwork operator is configured to utilize a first radio accesstechnology (RAT), and the source network operator is configured toutilize a second radio access technology (RAT).
 13. The system of claim12, wherein the first RAT comprises 5G, and the second RAT comprises anyof 4G, 5G, or 6G.
 14. The system of claim 13, wherein the target corenetwork node comprises any of an access and mobility management function(AMF) or a mobility management entity (MME).
 15. The system of claim 13,wherein the source core network node comprises any of an access andmobility management function (AMF) or a mobility management entity(MME).
 16. The system of claim 12, wherein the first RAT comprises 4G,and the second RAT comprises any of 4G, 5G, or 6G.
 17. The system ofclaim 16, wherein the target core network node comprises any of anaccess and mobility management function (AMF) or a mobility managemententity (MME).
 18. The system of claim 16, wherein the source corenetwork node comprises any of an access and mobility management function(AMF) or a mobility management entity (MME).
 19. A processing node forlimiting mobility, the processing node comprising a processor and amemory that enable the processing node to perform operations comprising:receiving, at a first core network node associated with a first radioaccess network (RAN), a first handover request from a second corenetwork node associated with a second RAN, the first handover requestbeing for a first wireless device on the second RAN; determining, by thefirst core network node, that a first cell identifier in the firsthandover request does not match an allowed list of cell identifiersassociated with a tracking area of the first RAN stored on the firstcore network node; and rejecting the first handover request.
 20. Theprocessing node of claim 19, wherein the first and second core networknodes are communicatively coupled via a N26 interface.